1. Technical Field
The present invention relates to waterproof hydrophilic, vapor permeable copolyetherester films that are flame resistant.
Copolyetheresters are well known and have enjoyed continued and increasing commercial success. These are especially useful resins because they are quite varied in consistency, ranging from a soft elastomer to semi-rigid plastics, and because they possess good overall properties, including superior tear strength, flex life, heat resistance, and toughness. In film form, they can be coated onto fabric to impart these improved properties to said fabric. However, copolyetherester resins and resin blends suffer from, and their applications are limited by, their high flammability. This flammability problem is intensified when the copolyetherester exists as a film since the ratio of surface area to the volume of the thin film is larger, thereby allowing more exposure to oxygen, which is needed to support combustion.
Various flame retardants have been added to copolyetheresters, or copolyester elastomers, in order to reduce or eliminate flammability. The level and type of flame retardant additives used depends upon the thickness of the object and the chemical and physical interactions between the additives and the copolyetherester. Flame retardants that are effective in copolyetherester resins are not necessarily effective in copolyetherester films. For example, some known flame retardants, when added to the copolyetherester elastomers and formed into films, are often ineffective in the film due to their lack of sufficient activity to control burning of the film, which has a high surface area and which is very thin. Some flame retardants effective in copolyetherester molded shapes resin are ineffective in a film because they actually interfere with the making of the film, i.e., the resultant film is of poor quality. Many solid flame retardants, which are effective in non-film forms of copolyetheresters, also have a substantial detrimental effect on the water vapor transmission rate of the copolyester elastomers and as such, result in film having poor water vapor transmission rates. The preceding statement holds true even when the copolyester elastomer contains a high degree of chemical groups, such as residues of ethylene oxides, which cause the copolyester elastomers to have the characteristic of being readily permeable to water vapor. Finally, many solid flame retardants interfere with the physical properties, such as elongation, of the copolyetherester.
These problems become particularly important in copolyetherester films because the films are thin articles, having a high ratio of surface area to volume, and therefore the films require higher levels of flame retardants than do thick articles. However, the more flame retardant added to the thin film, the more likely it will interfere with the physical properties and the processing qualities of the film. For example, as more of the flame retardant is added interaction between the additive and the hydrophilic groups in the copolyetherester elastomer polymer may occur, depending upon the chemical nature of the additive, and this interaction can decrease the water vapor transmission rate of the film. As a result of the above problems, there exists a need for a flame retardant that can be added to a copolyetherester elastomer such that a good film, in terms of appearance, can still be formed with the flame retardant present and such that the flame retardant imparts good flame resistant properties into the film, and finally, such that the flame retardant does not interfere substantially with the physical properties, such as elongation or water vapor transmission rate, of the film.
The present invention alleviates the above problems by providing a waterproof, hydrophilic, breathable copolyetherester film that has a water vapor transmission rate greater than 6000 gm.mil/m.sup.2 /24 hrs., that has an elongation of greater than 600 percent, and that has good flame retardant properties. These flame resistant copolyetherester elastomer film compositions can further be bonded to a woven, non-woven, or knit fabric, which is of a stretch or non-stretch nature, to impart to the fabrics the superior properties associated with copolyetherester elastomers while at the same time eliminating the flammability problems associated with said elastomers. Such fabrics include nylon, poly(ethylene-terephthalate), polyaramid, polyurethane, polypropylene, or polyethylene. They can also be bonded to a layer of a hydrophobic copolyetherester elastomer, as described in Applicant's U.S. Pat. No. 4,725,481, the disclosure of which is incorporated herein by reference, which in turn can be bonded to a woven, non-woven, or knit fabric which is of a stretch or non-stretch nature. The flame retarded copolyetherester elastomer film compositions, when bonded to fabric, can be used to make breathable, flame resistant, water vapor permeable clothing, such as raincoats, jackets, and fireman turnout coats. The films can also be used for tents and other equipment which require flame resistant characteristics.
2. Description of Related Art
U.S. Pat. No. 4,166,743, granted Sept. 4, 1979 to Wortmann et al., discloses an intumescent flame-retardant coating composition comprising a film-forming agent, which is an aqueous synthetic resin dispersion, an ammonium polyphosphate, a substance carbonizable under heat, such as dicyandiamide, pentaerythritol, or melamine, and a dispersant, such as water, ethyl acetate, butyl acetate, xylene, or toluene. The coating additionally contains an ammonium polyphosphate activator, said activator being constituted by at least one salt which contains water of crystallization which is liberated upon the composition being heated to 35.degree. C. to 250.degree. C. This reference teaches film-forming agents such as aqueous, synthetic resin dispersions and solutions in organic solvent but no melt extrudable polymers are mentioned.
U.S. Pat. No. 4,395,511, granted July 26, 1983 to Tschirch et al., discloses flame retarded polyurethane compositions, wherein the flame retardant is selected from the group consisting of the mixture of decabromodiphenyl oxide and antimony oxide and the mixture of decabromodiphenyl oxide, antimony oxide, and ammonium polyphosphate. There is no mention of copolyetherester films in this reference, nor is there disclosed the particular flame retardant agent claimed in the film of the present invention.
U.S. Pat. No. 4,521,557, granted June 4, 1985 to McKenna, discloses flame retardant copolyetherester elastomer compositions containing effective concentrations of N, N,-ethylenebis(tetrabromophthalimide), antimony trioxide, and fumed silica. European Patent Application 0 149 190, published July 24, 1985 by General Electric Company, discloses a flame retardant low-modulus copolyetherester composition which includes a flame retarding amount of, amongst other types of flame retardants, an aromatic carbonate copolymer in which from 25 to 75 weight percent of the repeating units comprise chloro- or bromo- substituted dihydric phenol units and the remainder of the repeating units comprise dihydric phenol, glycol, or dicarboxylic acid. U.S. Pat. No. 4,582,866, granted Apr. 15, 1986 to Shain, discloses flame retardant thermoplastic multi-block copolyester elastomer compositions containing a bromine-containing flame retardant, antimony trioxide, and an organophilic clay. While the above references all disclose flame-retarded copolyetherester compositions, none disclose a copolyetherester film which is made flame retardant and which maintains good water vapor transmission rates and elongation values.